I've got what I think you're referring to, but it was just another booklet with a lot of the same info repeated over and over again.
I didn't see any specific (i.e., individual) date and time in there, but I may have overlooked it.
I just went on mygophersports.com again and still it doesn't appear to be letting you test out the system yet (although you can for hockey). Where the materials sent in the mail say there will be a "Select Your Seats" section to click, the website has "Donate To Men's Basketball" instead.
In other words, I wouldn't sweat it. Doesn't appear that you can do anything at this point. Would have thought they would have had things setup before they sent this stuff out, but...